1. Field of the Invention
This invention relates to the field of medical diagnosis and treatment. More specifically, the present invention relates to a guidewire device for in vivo tissue diagnosis using electromagnetic energy and methods of using the guidewire device and diagnostic apparatus in conjunction with therapeutic catheters to diagnose and treat tissue in vivo.
2. Description of Related Art
Catheters used to treat and diagnose conditions within patients are known. Examples of such catheters include, but are not limited to, angioplasty catheters incorporating balloons to dilate a vessel, internal drug delivery catheters designed to deliver a drug to a localized area within a patient, laser ablation catheters designed to provide laser radiation within a patient's body for diagnosis and/or treatment, ultrasonic ablation catheters, thermal or mechanical disruptive catheters, stent delivery catheters, catheters for monitoring drug or other chemical concentrations/indications (e.g., pH) in vivo, and catheters for monitoring body functions (e.g., cardiac output).
The majority of catheters are designed to follow a guidewire inserted into the patient and are typically referred to as "over-the-wire" catheters. A subset of those catheters are referred to as "rapid-exchange" catheters. Guidewires are used with catheters because they are typically very flexible and have a smaller diameter than the catheters used for diagnosis and/or treatment. Guidewires are also typically steerable, allowing the physician to better direct the guidewire as it is advanced through the patient. Because of their flexibility, steerability and small diameter, guidewires can be directed to places within a patient that the succeeding catheter could not reach without following the guidewire. In some cases, guidewires can reach locations which no catheter could reach. Guidewires are also typically radiopaque to allow monitoring of their position through standard fluoroscopic techniques.
In use, the guidewire is advanced to the desired position within a patient. In the case of a blood vessel in which a stenosis or occlusion exists, the guidewire is advanced past the stenosis or occlusion and remains in place as the diagnostic and/or therapeutic catheter is advanced to the site of the lesion. The catheter typically contains a lumen, or passageway, through which the guidewire passes as the catheter is advanced along it.
Guidewires are generally known in the art. U.S. Pat. No. 4,545,390 describes a guidewire having a relatively long wire having a proximal end, and a distal end. A relatively short helically wound spring is connected to the distal end which can be bent to retain a curve and is sufficiently flexible to follow a blood vessel without traumatization. The wire is sufficiently torsionally rigid to transmit angular rotation from the proximal end to the distal end to aid in steering the guidewire. In U.S. Pat. No. 4,554,929 a safety wire interconnects the wire and the coil. In U.S. Pat. No. 4,619,274, a core element decreases in diameter from its proximal end to its distal end, and a helical coil has a diameter that decreases toward its distal end, the coil being formed of a wire whose diameter decrease, with the larger diameter being at the proximal end. In U.S. Pat. No. 4,721,117, a tubular heat-shrinkable jacket covers the wire. In U.S. Pat. No. 4,748,986, the wire has a tapered intermediate portion, and a flattened distal portion. A coil surrounds the wire, and a safety wire interconnects the wire and the coil.
Catheters containing optical fibers are generally known in the art. U.S. Pat. No. 4,648,892 describes a catheter having an optical shield at the distal end of the catheter. In U.S. Pat. No. 4,669,465, an interlock is provided to prevent operation of a laser until the end of a beam transmitting fiber extends beyond the distal end of the catheter. In U.S. Pat. No. 4,669,467, the ends of a bundle of optical fibers are stressed in order to mix the modes of the optical fibers. Laser catheters are often designed to be introduced over a guidewire which has previously been inserted into a patient.
It is known to analyze radiation that is received from tissue as a result of illumination of the tissue by the use of a catheter. U.S. Pat. No. 4,718,417 describes illuminating tissue with radiation that is generally in the 480 nm range, and then analyzing reflected radiation, generally in the range of 520 to 610 nm, in order to distinguish between healthy tissue and other material, such as plaque. In U.S. Pat. No. 5,104,392, the device operates to continue to ablate a tissue mass until a characteristic returned optical signal is no longer received therefrom. In U.S. Pat. No. 5,106,387, a catheter is used to illuminate a tissue mass to thereby induce fluorescence of the tissue. The returned fluorescence is then analyzed in order to diagnose the tissue mass. All of the above-listed patents are incorporated herein by reference for their teachings relating to diagnosis and treatment of tissue.
One disadvantage of all of the above described systems is the absence of a diagnostic tool to allow the physician to identify the tissue at the treatment site before inserting a separate catheter to diagnose the tissue and/or treat it. The alternative is to eliminate the diagnostic step and provide treatment designed for many different tissues and conditions, but which, in reality, is likely not optimized for any particular tissue or condition.
Another alternative is to provide separate catheters for diagnosis and treatment. That alternative can, however, increase the cost and complexity of the procedure.
Furthermore, exchanging catheters increases the time required to complete the procedures and also increases the risk, or morbidity, associated with the procedure.
Another disadvantage is that some of the known laser catheters are not suited for percutaneous delivery as are most balloon angioplasty and localized drug delivery catheters. As a result, the trauma associated with introducing the catheters is increased over those devices designed for percutaneous administration.